Conventionally, a synthetic resin fastener element formed one by one by injection molding a synthetic resin to a fastener tape, a continuous fastener element formed by molding a mono filament in a coil shape or in a zigzag shape, a metal fastener element formed by caulking a metal element material exhibiting an approximately Y-shape to a fastener tape, and the like are known as a fastener element used in a slide fastener.
The synthetic resin fastener element is generally molded so as to stride across a tape front surface that is a first surface of the fastener tape and a back surface that is a second surface of fastener tape and has an element upper half portion disposed to a tape front surface side of the fastener tape and an element lower half portion disposed to a back surface side of the fastener tape.
Further, although in many cases the synthetic resin fastener elements are molded so that the element upper half portion and the element lower half portion are formed in a symmetric shape, the element upper half portion and the element lower half portion may be formed in an asymmetric different shape to improve, for example, beauty and a feeling of touch (property perceived by touch) of a fastener element.
An example of the fastener element having the shape in which the element upper half portion is different from the element lower half portion as described above is disclosed in, for example, WO 2010/082294 A (Patent Document 1), and the like.
Here, the synthetic resin fastener element described in Patent Document 1 will be explained referring to FIG. 9. Note that, in the following explanation, a tape length direction of the fastener tape is prescribed as a front/back direction. Further, a tape width direction of the fastener tape is prescribed as a right/left direction, and a tape front/back direction of the fastener tape is prescribed as an up/down direction.
A fastener element 60 of Patent Document 1 has an element upper half portion 61 disposed to a first surface side of a fastener tape 70 and an element lower half portion 62 disposed to the second surface side of the fastener tape 70. The element upper half portion 61 includes a first tape sandwiching portion 61a for sandwiching the fastener tape 70 between the first tape sandwiching portion 61a and the element lower half portion 62, and a first head portion 61b in a tapered form extending from the first tape sandwiching portion 61a toward external of the tape.
The first tape sandwiching portion 61a in the element upper half portion 61 and a part of the first head portion 61b are provided with front and back taper portions 61c, which gradually decrease a dimension of the element upper half portion 61 in a front/back direction toward upward, on front and back side surfaces. The disposition of the front and back taper portions 61c can cause an outside appearance of the fastener element 60 to be viewed as if it is a metal fastener element 60 when the fastener element 60 is viewed from a front surface side. Further, since the provision of the element upper half portion 61 with the front and back taper portions 61c can more increase a dimension of the first tape sandwiching portion 61a at its lower end in an up/down direction (element width dimension) than its upper edges, a fixing strength of the fastener element 60 to the fastener tape 70 can be increased.
Further, the first head portion 61b in the element upper half portion 61 is formed in a taper shape so that a dimension of the first head portion 61b in the tape length direction gradually decreases from a base end portion joined to the first tape sandwiching portion 61a toward an forefront portion. With the configuration, the outside appearance of the fastener element 60 can be made further closer to the metal fastener element 60.
The first head portion 61b is configured to swell in the front/back direction than a neck portion 62b to be described later of the element lower half portion 62. With the configuration, even when the right/left fastener elements 60 receives a force for pushing them up from a lower direction to an upper direction, since the first head portion 61b can support the element lower half portion 62 (in particular, a second head portion 62c to be described later) that is a engagement opponent, an occurrence of the engagement failure (also referred to as chain failure) can be prevented from being occurred and a engaged state of the fastener element 60 can be kept stable.
Further, the element upper half portion 61 is formed with an upper taper portion 61d, which inclines downward to gradually decrease a height dimension of the fastener element 60 in the up/down direction toward an forefront portion of the first head portion 61b, as an interference avoiding portion to be described later.
The element lower half portion 62 of the fastener element 60 is formed integrally with the element upper half portion 61. The element lower half portion 62 includes a second tape sandwiching portion 62a for sandwiching the fastener tape 70 between a second tape sandwiching portion 62a and the first tape sandwiching portion 61a of the element upper half portion 61, the neck portion 62b extending from the second tape sandwiching portion 62a toward external of the tape and having a shape narrowed in the front/back direction, and the second head portion 62c disposed at an forefront portion of the neck portion 62b and swelling in the front/back direction.
Note that, in Patent Document 1, when the right/left element rows are engaged, since the right/left fastener elements 60 are engaged with each other only in the element lower half portion 62, engaging strength becomes weak as compared with an ordinary type fastener element having a shape in which the element upper half portion 61 is in symmetry with the element lower half portion 62.
Since the slide fastener according to Patent Document 1 which is configured such that the synthetic resin fastener elements 60 having the configuration described above are disposed to the fastener tape 70 side by side exhibits an outside appearance as if the respective fastener elements are metal fastener elements 60 when viewed from the front surface side, the slide fastener is excellent in outside appearance quality and a design property.
Further, in the slide fastener, the upper taper portion 61d described above is formed to the element upper half portion 61 of the fastener element 60 of each of the fastener elements as an interference avoiding portion. Accordingly, when the slide fastener is bent to the tape first surface side so that the element upper half portions 61 approach each other in the engaged state of the fastener element 60, the first head portions 61b of the respective fastener elements 60 can be prevented from interfering with the element upper half portions 61 of the engagement opponent.
To explain more specifically, when the slide fastener is bent in a direction where the element upper half portions approach each other in the engaged state of the fastener element at, for example, the time that the upper taper portion 61d as in Patent Document 1 is not disposed to the element upper half portion 61, the first head portion of the element upper half portion interferes with the element upper half portion of a engagement opponent side, and the element lower half portions of the fastener elements adjacent to each other on the engagement opponent sides are turned in a direction where they are away from each other using the interfering portion as a fulcrum. As a result, a large expansion of the interval between the second head portions of the fastener element causes the right/left fastener elements to disengage, from which a problem arises in that chain failure occurs.
In contrast, in Patent Document 1, the disposition the upper taper portion 61d to the element upper half portion 61 of the fastener element 60 prevents the element upper half portion 61 of the engagement opponent side from interfering with the first head portion 61b of the fastener element 60 when the slide fastener is bent to the tape first surface side as described above.
In the case, since the element upper half portions 61 adjacent to each other in the tape length direction come into contact with each other before the right/left fastener elements 60 are released from a engaged state, so that a bent amount of the slide fastener can be regulated. Accordingly, in the slide fastener according to Patent Document 1, even if the slide fastener is bent in an U-shape, since the second head portions 62c of the fastener elements 60 can be prevented from being away from each other until the fastener elements 60 are released from the engaged state, a problem that the chain failure occurs to the element row as described above can be overcome.
Incidentally, also known as the conventional slide fastener are a type of a slide fastener which can be opened from both end sides of an element row in a length direction and a type of a slide fastener which can be closed from both end sides of an element row in addition to an ordinary slide fastener of a type in which the slide fastener can be opened or closed from an end side toward other end side of an element row in a length direction.
For example, in the ordinary slide fastener, a separable bottom end stop is composed of an insert pin attached to an end of a fastener stringer and a box pin and a box attached to an end of the other fastener stringer. Hereinafter, the separable bottom end stop will be called a one side separable bottom end stop.
In contrast, the slide fastener which can be opened from both the end sides of the element row is disclosed in, for example, JP 2006-346364 A (Patent Document 2) and the like, has two sliders slidably disposed along an element row with rear ports facing each other, an insert pin attached to an end of a fastener stringer, and a box pin attached to an end of the other fastener stringer, and a separable bottom end stop is composed of the two sliders, the insert pin, and the box pin. Hereinafter, the separable bottom end stop will be called a both sides separable bottom end stop.